Musical instrument soundboard system



' M y 1970 H. K. GRAVES 3,511,125

MUSICAL INSTRUMENT SOUNDBOARD SYSTEM Filed March 27, 1967 Q 2 Sheets-Sheet 1 I I L May 12, 1970 H. K. GRAVES 3,511,125

MUSICAL INSTRUMENT SOUNDBOARD SYSTEM I Filed March 27, 1967 2 Sheets-Sheet 2 INVENTOR.

' Han/4 00 44 67944 65 United States Patent 3,511,125 MUSICAL INSTRUMENT SOUNDBOARl) SYSTEM Howard K. Graves, 6633 Somerset Drive, Cleveland, Ohio 44141 Continuation-in-part of applications Ser. No. 501,661,

Oct. 22, 1965, and Ser. No. 528,908, Feb. 21, 1966. This application Mar. 27, 1967, Ser. No. 626,295

Int. Cl. G10c 3/06 US. Cl. 84192 3 Claims ABSTRACT OF THE DISCLOSURE A stringed musical instrument comprising a soundboard system which includes a frame, strings, a bridge, and a soundboard. A soundboard system with stillness at the bridge which is essentially that of the strings. A soundboard which has an integral rigidizing contour. A soundboard that has an edge portion extending transversely of of the strings tightly coupled to the frame and an opposed edge portion loosely coupled. The bridge extends along the loosely coupled edge.

The present application is a continuation-in-part of my co-pending applications Ser. Nos. 528,908 and 501,661, filed Feb. 21, 1966 and Oct. 22, 1965, respectively, now Pat. Nos. 3,311,009 and 3,312,136.

An important object of the present invention is to provide a new and improved soundboard system for a stringed musical instrument in which the stiffness of the soundboard is comparatively small or is reduced to a minimum.

Another object of the present invention is to provide a soundboard system for a stringed musical instrument, such as a piano, where the stillness of the system at the bridge is comparatively small or is reduced to a minimum.

A still further object of the present invention is to provide a new and improved stringed instrument, such as a piano, in which a soundboard has opposed edges and strings extending transversely over the opposed edges with the soundboard being tightly coupled to the frame along one of the opposed edges and loosely coupled to the frame along the other of the opposed edges with the strings being connected to the soundboard by a bridge, each string being tensioned such that it does not supply a force tending to move the bridge and the stillness of the system as the bridge being essentially provided by the strings.

Other objects and a fuller understanding of this invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings in which:

FIG. 1 is a plan view of a piano soundboard system;

FIG. 2 is a sectional view along line 22 in FIG. 1 showing a soundboard that is mounted so that it may vibrate in a generally angular manner;

FIG. 3 is an enlarged sectional view along line 33 in FIG. 1 showing the engagement of the strings with the bridge;

FIG. 4 is an enlarged sectional view along line 44 in FIG. 2 showing the cross section of the soundboard;

FIG. 5 is an enlarged sectional view along line 3-3 in FIG. 1 showing a supplementary mass weight secured to the bridge.

FIGS. 6A6E are enlarged sectional views showing a range of different methods by which the soundboard may be mounted.

Referring to the drawings, FIG. 1 and FIG. 2 show a plan view and a cross-section view respectively of a piano soundboard system constructed in accordance with the principles of this invention. A soundboard system is comprised of a frame, a complement of musical strings, a bridge, and a soundboard. A piano frame 10 is a strong,

rigid structure that is preferably made from cast iron. Frame 10 tensionally supports a complement of musical strings indicated in general by numeral 11. The length, diameter, tension, and number of strings per note are determined from empirical relationships that are well known by those skilled in the art of string scaling. FIG. 1 shows only one string per note and the strings that are shown are merely representative of the full complement of musical strings.

Strings 11 are secured at one end to hitch pins 12, which, in turn, are anchored to the lower portion 13 of frame 10. The other end of strings 11 is secured by wrapped engagement to tuning pins 14. Tuning pins 14 are secured by means of tuning pin bushings 15 to the upper portion 16 of frame 10. The tension in strings 11 is adjusted by rotating tuning pins 14 in tuning pin bushings 15.

One of the vibration ends of the strings 11 is formed by the raised capo dastro rib 17 on the upper portion 16 of frame 10. The other vibration end of the strings 11 is formed by bridge 19 which is a generally S-shaped member that traverses the strings and is coupled to the strings. The strings 11 vibrate between rib 17 and bridge 19. The strings 11 are coupled to bridge 19 by means of bridge caps 20 that are shown in detail in FIG. 3. The strings or strings comprising each note are secured to the bridge 19 preferably by separate bridge caps. The bridge caps that are shown in FIG. 1 are merely representative of the full complement of bridge caps. Bridge cap 20 is comprised of an E section with outside flanges 21 and 22 and an inside bearing flange 23. The strings 11 p ss through holes int he two outside flanges 21 and 22, and the strings are displaced by bearing flange 23 so that the strings make positive vibrational engagement with bridge cap 20. Bridge cap 20 is secured as with adhesive to bridge 19. Bridge 19 is coupled to soundboard 24 as with adhesive at contact surface 30. Thus soundboard 24 is cou led to the vibrational end of strings 11.

The strings 11 are set into vibration by means of a blow from a piano hammer, not shown. The vibration of the strings is transmitted to the air by means of soundboard 24 which is vibrationally coupled to strings 11. The character of the tone that is produced by the soundboard system is dependent upon the velocity, or the amplitude, with which the strings are permitted to vibrate at the bridge. If the velocity of vibration at the bridge is too small, the energy of the strings will be transferred too slowly to the air and the tone of the soundboard system will be thin and weak. If the velocity of vibration at the bridge is too large, the energy of the strings will be transferred too rapidly to the air and the tone of the soundboard system will sound like a nonmusical thud. An optimum velocity of vibration at the bridge produces the most pleasing musical tone.

The soundboard system of a conventional musical instrument, such as a piano, has significant degrees of both mass and stillness. The mass at the bridge of a conventional soundboard system includes the mass of the soundboard and the mass of the bridge. The stillness at the bridge of a conventional soundboard system includes the stillness of the soundboard and the stillness of the strings.

In my earlier soundboard inventions, I found that an improved tonal sensitivity could be achieved by separating the means for radiating sound from the means for providing stillness at the bridge. I found that supplying the stillness at the bridge by a separate stiffness means permitted me to use a soundboard that was a light, responsive, eflicient radiator of sound. I have more recently found that a further improvement in tone quality may be obtained by reducing the stillness at the bridge to a practical minimum.

The stiffness of the soundboard system at the bridge is generally comprised of the stiffness of the soundboard at the bridge and the stiffness caused by the ends of the strings between the bridge and the hitch pins. The stiffness of the soundboard at the bridge may vary based upon the structural stiffness of the soundboard and the method of mounting the soundboard to the frame. However the stiffness of the string ends is generally dependent upon the length of the string ends and string to string vertical bearing tolerances, so that the stiffness of the string ends cannot be reduced below a practical minimum. Thus the minimum stiffness of the system at the bridge that can be achieved is the stiffness at the bridge of the string ends.

FIG. 2 shows that the strings 11 are straight between hitch pins 12 and capo dastro rib 17. The strings do not have vertical bearing against bridge 19 because a soundboard With relatively small stiffness is not capable of supplying any significant bearing force against the strings at the bridge. Conversely, an instrument that has, or is capable of having, vertical bearing of the strings against the bridge must have a soundboard with significant stiffness, and therefore such an instrument cannot have a soundboard of relatively small stiffness at the bridge. The soundboard system of the present invention is also free from appreciable external stiffness.

In the preferred embodiment of this invention, the soundboard contributes comparatively little stiffness or mass at the bridge and the soundboard is a light, efficient, responsive sound radiator.

Such a soundboard is shown in FIG. 4. Soundboard 24 is preferably a member that is sufficiently rigid to drive air yet is sufficiently light to faithfully respond to the tone quality of the strings 11. The light weight soundboard 24 has an integral rigidizing contour to increase its rigidity to enable it to be a good sound radiator. The integral rigidizing contour may be provided by reversely folding the member along substantially parallel lines, as in the preferred embodiment, to provide corrugations that are somewhat parallel with the strings 11. The integral rigidizing contour may also be provided by ribs, grids and the like formed into the material. The soundboard may be made from a variety of materials such as wood, metal, plastic, foamed plastic, or paper. I have found that heavy manila paper, when formed into the corrugated shape shown, makes a good sound radiator. The thickness of the paper and the spacing and depth of the corrugations may be varied across the soundboard to achieve an optirnum tonal response to the range of frequencies being radiated in that portion of the soundboard. The various areas of the soundboard may thus be made to respond to specific ranges of frequencies in much the same way as the tweeter, mid-range and woofer loud speakers in a loud speaker system together reproduce the complete audio spectrum.

The mass at the bridge may be varied along the length of the bridge. In adjusting the mass at the bridge to achieve the proper gradation of mass, supplementary mass weights may be secured to the bridge as shown in FIG. 5. Supplementary mass weights 36 are vibrationally secured to bridge caps 20 by means of screws 35.

In the preferred embodiment of this invention, the soundboard is supported in a cantilevered manner such that it may vibrate, at least in a fundamental mode of vibration, in a somewhat angular manner. In FIG. 2, the soundboard 24 is tightly coupled to frame along edge 25 that is adjacent to the hammer strike line, and is loosely coupled to frame 10 along the edges 27, 28, and 29 that are adjacent to the bridge. The soundboard 24 is rigidly secured as with adhesive to the raised portion 26 on the upper portion 16 of frame 10, and is freely suspended along the edges 27, 28, and 29. A cantilevered soundboard, besides being freely suspended along its loosely coupled edges, may be compliantly coupled to the frame along its loosely coupled edges as shown in FIG. 6D. A comparativelysmall degree of stiffness of soundboard at 4 the bridge may be provided by the flexure of the soundboard at the tightly coupled edge and by the structural fiexure of the soundboard.

FIGS. 6A6E summarize different methods of mounting a soundboard to a frame. The methods of mounting a soundboard may include more than one type of coupling as is true in the mounting shown in FIG. 2, and in any one soundboard system more than one soundboard may be used. In FIGS. 6A6E the soundboard is shown as coupled to a portion 16 of a frame 10. In FIG. 6A a soundboard 24- is rigidly coupled along its edge 25: as with adhesive to a raised portion 26 of frame portion 16. The rigid coupling at edge 25' substantially prevents the edge of the soundboard from rotating or translating. In FIG. 6B the soundboard 24 is pivotally coupled to frame portion 16' by means of flexural pivot 41. Flexural pivot 41 is preferably made from a thin, resilient material. The soundboard 24 is secured as with adhesive to flexural plvot 41, which in turn is secured as with adhesive to frame portion 16. The flexural pivot 41 allows soundboard 24 to move angularly in a free manner about its edge but substantially rigidly restrains movement of the edge m a direction perpendicular to the plane of the soundboard. FIG. 6C shows a stiff coupling between soundboard 24 and frame portion 16. Soundboard 24 is secured as with adhesive to stiff member 42, which in turn is secured as with adhesive to frame portion 16. Stiff member 42 allows soundboard 24 to rotate and translate about its edge 25' in a greatly restrained manner. FIG. 6D shows a compliant coupling between soundboard 24 and frame portion 16. Soundboard 24 is secured as with adhesive to compliant member43, which in turn is secured as with adhesive to frame portion 16. Compliant member 43 may be made from any suitable material such as paper, cloth, plastic or the like. Compliant member 43 allows the edge 25 of soundboard 24 to rotate and translate normal to its surface with little restraint. FIG. 6E shows a freely suspended edge of soundboard 24 with an air gap 44 between soundboard 24 and frame portion 16, so that the soundboard is not physically attached to the frame.

The relative gradations of tightness and looseness of the coupling of the edge of the soundboard to the frame are, in decreasing order of tightness: rigid (FIG. 6A), pivoted (FIG. 6B), stiff (FIG. 6C), compliant (FIG. 61?), and free (FIG. 6B). A rigid, pivoted, or stiff coupling is a relatively tight coupling, and a compliant or free coupllng is a relatively loose coupling.

This invention has been disclosed as being applicable to a piano, but it will be apparent to one skilled in the art that the invention is also applicable to other stringed Il'lllSlcal instruments. Moreover, it will also be appreciated that the cantilevered soundboard with its free edge loosely or compliantly coupled to the frame is adopted for use 1n systems which are not essentially mass controlled and with relatively rigid soundboards.

It will herein be understood, of course, that these embodiments of the invention have been used for illustrative purposes only and that various modifications and variations in the present invention may be affected without departing from the spirit and scope of the novel concepts thereof.

What is claimed is:

1. In a stringed musical instrument, a frame, a plurality of strings on said frame, a soundboard system for said strings comprising a soundboard, bridge means coupling said strings to said soundboard, the stiffness of said system at said bridge being predominantly that provided by said strings, and mounting means on said frame at opposite ends of said strings for tensioning said strings on said frame such that the tensioning forces acting between each string and the bridge have substantially no component tending to cause said bridge means to move in a direction perpendicular to said soundboard, said bridge means exnding transversely of said strings adjacent a first edge p on of said soundboard adjacent one end of said strings and said soundboard having a second edge portion opposed to said first edge portion extending transversely of said strings adjacent the other ends of said strings, said first edge portion at said one end of said strings being loosely coupled to said frame, said instrument including connecting means along said second edge portion tightly coupling said soundboard to said frame and constraining said second edge portion against movement laterally thereof and said soundboard to move angularly thereabout.

2. A piano having a frame, a soundboard systemcomprising a soundboard, said soundboard having opposed first and second edge portions, a plurality of strings tensioned on said frame and extending transversely of said edge portions, a bridge extending transversely of said strings and coupling said strings to said soundboard, said soundboard system having a stiffness at said bridge which is essentially that provided by said strings, mounting means on said frame at opposite ends of said strings for tensioning said strings on said frame such that the tensioning forces acting between each string and said bridge have substantially no component tending to move said bridge in a direction perpendicular to said soundboard, said bridge extending along said first edge portion of said soundboard, said strings having a hammer strike line extending transversely of said strings, said hammer strike line extending transversely of said strings adjacent said second edge portion, connecting means along said second edge portion for tightly coupling said soundboard to said frame along said second edge portion and constraining said second edge portion against movement laterally of said second edge portion to thereby constrain said soundboard to move angularly about said second edge portion, said soundboard being loosely coupled to said frame along said first edge portion.

3. A stringed instrument comprising a frame, a soundboard system comprising a soundboard, said soundboard having opposed first and second edge portions, a plurality of strings tensioned on said frame and extending trans- 'versely of said edge portions, a bridge extending transversely of said strings and coupling said strings to said soundboard, said soundboard system for said strings having a stiffness at said bridge which is essentially that provided by said strings, mounting means on said frame at opposite ends of said strings for tensioning said strings on said frame such that the tensioning forces acting between each string and said bridge have substantially no component tending to move said bridge in a direction perpendicular to said soundboard, connecting means along said second edge portion for tightly coupling the second edge portion to said frame along said second edge portion and holding the second edge portion against lateral movement, said soundboard being loosely coupled to said frame along said first edge portion.

References Cited UNITED STATES PATENTS 12,362 2/1855 Gray 84l92 191,587 6/1877 Herald 84213 215,089 5/1879 Brewer 84213 3,311,009 3/1967 Graves 84l92 3,312,136 4/1967 Graves 84l92 2,229,440 1/ 1941 Carlisle 84l92 3,236,138 2/1966 Graves 84l92 RICHARD B. WILKINSON, Primary Examiner J. F. GONZALES, Assistant Examiner 

